Descriptive characteristics of the included studies, presented as those that were meta-analysed and those that were descriptively summarised (n=67 studies)
| Meta-analysed | Narrative | |
| N reporting (/49) | N reporting (/18) | |
| Sample size (n) | ||
| <100 | 9 | 7 |
| 100–499 | 22 | 6 |
| 500–999 | 7 | 1 |
| >1000 | 11 | 4 |
| Age at baseline (n) Mean (SD) years | 15.6 (1.4) | 15.8 (1.5) |
| Length of follow-up (n) Mean (SD) years | 3.4 (2.6) | 3.8 (3.0) |
| Region (n) | ||
| Europe | 20 | 10 |
| North America | 22 | 5 |
| LMIC | 3 | 0 |
| Other HIC | 4 | 3 |
| Ethnicity (n) (% white Mean(SD)) | 20 69.3 (26.6) | 5 72.1 (16.3) |
|
SES (n) (% mothers with college degree Mean(SD)) | 9 39.7 (16.4) | 2 46.5 (12.0) |
SES expressed as % mothers with college degree (the most commonly reported measure).
HIC, high-income countries; LMIC, low-income and middle-income countries; SES, socioeconomic status.